Thermal redistribution of compressive residual stress introduced by interlayer laser shock peening in hybrid additive manufacturing

Abstract

The objective of this research was to quantify the change in magnitude and depth of compressive residual stress (CRS) retained in the subsurface by interlayer coldworking when subjected to localized annealing that superimposed tensile stress. The approach was to hybridize additive manufacturing of AlSi10Mg alloy by coupling powder bed fusion (PBF) with laser shock peening (LSP) and characterize the resultant residual stress state by the hole-drilling method. The research found localized annealing from layer deposition formed two distinct regions in the subsurface, which was driven by localized and bulk stress redistribution. The experiments also showed that residual stress redistribution from LSP reached 550 µm into the subsurface, whereas local annealing from the deposition of layers extended only to a depth of 160 µm. Hence, compressive stress imparted by LSP was not entirely canceled by local annealing from PBF. This work provides the first quantification of the stress state response of hybrid additively manufactured parts to thermal loads and is fundamental to improving part performance through increased functional reliability, fatigue life, and corrosion resistance.